<form class="login">
    <div class="form-group">
        <label for="exampleInputEmail1">请输入手机号码:</label>
        <input type="text" class="form-control" id="exampleInputEmail1" aria-describedby="emailHelp">
        <small id="emailHelp" class="form-text text-muted" hidden>We'll never share your email with anyone else.</small>
    </div>
    <button type="button" class="btn btn-secondary formButton"
        onclick="send_sms(document.getElementById('exampleInputEmail1').value)">获取验证码</button>
</form>